1. Field of the Invention
The present invention relates to a method and apparatus for selection of an elevator in an elevator group.
The elevators in an elevator group should be laid out so that the distances between the elevators be as short as possible to allow the passengers to traverse the distance to that elevator whose door is opened in a short time, thus allowing the doors to be closed as quickly as possible. For architectural reasons, this is not always possible, and the distances between elevators should be increased due to many factors, such as the presence of stairs or equivalent between the elevators.
Moreover, in the case of elevator groups with several elevators placed oppositely, the space between the elevators is often furnished with flowers, chairs, etc. Thus, a passenger waiting for an elevator must get around these obstacles if an elevator on the other side of the lobby arrives first. This must be taken into consideration in the control of the elevator group by using longer door-open times, which leads to a considerable loss of transportation capacity as the doors are often kept open longer than necessary.
An elevator group should be so structured that, dimensioned in accordance with common practice, it would be capable of transporting all the passengers even during busy rush hours without the passengers having to line up at the landings. For many reasons, this is generally not the case in large elevator groups. One of the main reasons is that during peak traffic in large elevator groups a small number of passengers travel in the direction opposite to the prevailing peak traffic direction. These passengers usually travel one by one, and keeping the doors open for an unduly long time for them means a considerable decrease in the transportation capacity at a time when it is desirable to use all the available capacity as efficiently as possible to cope with the peak traffic.
In the case of a large elevator group, which in this context means five or more elevators working under the same group control system and serving the same floors, the elevator lobby should be made large enough to allow the passengers to wait and walk freely, without delays caused by insufficient space. This means that the distances between the outermost elevators should be large. Thus, the time for opening the doors for single passengers during peak traffic must be very carefully optimized, otherwise the transportation capacity will be reduced even more significantly due to the longer door-open times required by the size of the lobby and to the longer door-close times caused by the large size of the doors generally used in large elevator groups.
It is known that, in the determination of the transportation capacity of an elevator group, about one third of the time available to an elevator is dependent on the passengers' walking to the doors and in the door area. Thus, improving the efficiency of door operations has a significant effect on the operation of the elevator group as a whole. Another fact restricting the transportation capacity in the case of large elevator lobbies is that the passengers waiting for an elevator form a disordered, scattered crowd in front of the elevators.
In some previously known procedures, passengers who desire to travel in a direction opposite to the direction of the main traffic during heavy peak hours are not served at all for determined short periods, e.g. five minutes, or the standard of service offered to these passengers is lowered intentionally by employing various control principles, e.g. by allowing only one elevator to serve calls for transport in the opposite direction. In the latest microcomputer-based systems, the priorities of calls for transport in the direction of the peak traffic may be intensified with respect to calls for transport in the opposite direction. In business buildings, this is naturally a hindrance to the activities.
Further inconveniences appear from the fact that some passengers who have to wait longer than the others may become too impatient to wait and they intentionally enter a car travelling in the undesired direction, reckoning that they will get faster to the destination by going first in the opposite direction and then back in the desired direction. This practice places an unnecessary additional load on the transportation capacity of the elevator group.
In some of the current procedures, this problem is taken into consideration in the development of the principles for controlling elevator groups by allowing the group control decide at a very early stage which elevator will serve which floor. On the basis of this decision, the system performs a so-called advance signalling, which in this context means that the passengers are informed in good time which elevator is arriving, by means of signalling devices provided on the floors, e.g. by blinking the appropriate direction arrows at the landings. As the elevator starts decelerating, after the group control system has made the irrevocable decision that the elevator shall stop, a final arrival signal is given e.g. with a continuous light in the direction arrow. In some situations, however, the operation of the system may depart from the advance signalling in as many as over 20% of the cases.
This results in a considerable drawback because departures from the advance signalling cause confusion when the passengers waiting in the lobby after all have to use an elevator other than the one indicated by the advance signalling. A further drawback is that a cancellation after the advance signalling require additional time for the passengers to walk to another elevator after they had already gathered in front of the advance signalled elevator. Thus, the distance to another elevator may be still longer.
To eliminate the reduction in the transportation capacity resulting from long door-open times, a currently used procedure employs a door control system in which the length of the basic door-open time is set to a value depending on the dimensions of the lobby, but when an electric eye placed in the door opening indicates that passengers are entering the car, the door-open time for subsequently entering passengers is shortened considerably. People travelling in a group easily notice each others moves. Those standing close will reach the door soon enough, whereafter even the slow persons have enough time to reach the car although the door times have been adjusted to a low value. This principle works fairly well in up- or down-peak situations in large business buildings, where it does not take long for few passengers to gather in the lobby. However, in the case of single passengers, a considerable loss of time still can not be avoided. In the internal traffic in a building, this procedure does not bring any noticeable advantage.
Furthermore, all the above-mentioned solutions have the common drawback that they are based on the assumption that single passengers follow the advance signalling. However, passengers travelling alone pay particularly little attention to the signalling. Also, old people, invalids and children often do not act according to the assumptions regarding passenger behaviour on which the solutions referred to are based.